Calcium is a ubiquitous element that occurs commonly in nature both in soluble (calcium chloride, sea water) and insoluble (gypsum, limestone) forms. It is a macronutrient essential to all life forms.
Apart from calcium being vital for proper bone and teeth formation (approximately 99% of calcium found in the animal are in bones and teeth), it also functions in transmission of nerve impulses and contraction of muscle tissue. Because of its importance in bone structure, deficiency of calcium in young animals leads to skeletal deformation. In older animals, similar to older human beings, fragile bone can result from extended periods of dietary calcium deficiency. Calcium is also needed for the blood clotting process for animals; and many enzymes present in an animal's body require calcium for their activities. Age, size, sex and physiological state of the animals determine their calcium requirement.
Comprising about 1.5% of a bird's weight, calcium is the predominant mineral in its body. Similar to other animals, calcium in a bird's body is used for bone formation, blood clotting, muscle and nerve function, and for the activation of enzymes. It also effects the formation of eggshells.
For animals, critical times to ensure that diets contain adequate calcium are during pregnancy (for proper growth of the fetus) and during lactation (to prevent excessive calcium mobilization from the bones of the lactating animals). Animals in full lactation draw on the calcium reserves in bone for manufacturing of milk. During this period, a tremendous amount of calcium is drawn into colostrums and milk. As a result, the animal's blood can become deficient in calcium and onsets Milk Fever.
The chick's requirements for calcium constitute only a small percentage of the total diet (0.6%). The growing chicks, unlike young mammals that receive their calcium from milk, are most sensitive to low levels of calcium up to 3 weeks of age. After this, their tolerance to the low levels of calcium increases. However, too little calcium can cause demineralization of bone (fracturing), soft eggshells, and inadequate calcium levels in the blood. Diets that are deficient in calcium are supplemented with calcium in drinking water or mixed with the seeds. When the bird enters egg production, her need for calcium more than triples in order to support shell formation. Clearly, at this time a source of calcium supplement is needed.
The soluble calcium salts, including calcium chloride which is the most prominent, present problems: liquid forms of these salts create bulk for shipping and storage purposes because of their high water content (65% to 70% H2O). Anhydrous soluble calcium salts (90% to 95% CaCl2), however, are hygroscopic and deliquescent, i.e. they absorb water to the point that the salts dissolve, creating even more long term shipping, storage and handling problems. Commercial solutions of calcium chloride and urea, the urea added to provide nitrogen in the conditioning process, are also available. Disadvantages of these solution products include their high water content, which increases weight and therefore increases the cost of transportation, and storage per unit of calcium. Extra equipment and costs are necessary because solutions require that liquid application devices be used.
The problem associated with providing dry, granular soluble calcium-containing products is the moisture-absorbing characteristics of these products. As mentioned above, the hygroscopic and deliquescent properties associated with the anhydrous soluble calcium salts and some of their hydrates create storage, handling and usage problems. Frequently, moisture is absorbed by the stored salt and converts the initially free-flowing salt to a solid rock-like mass. This severely limits the shelf life, creates handling and disposal problems that often lead to damaged goods, extra expenses, and sometimes-total loss of the product.
Unfortunately, admixtures of hygroscopic calcium salts with nutrients do not avoid the moisture uptake problem. For example, calcium chloride and urea form an adduct that is at least as or even more hygroscopic than calcium chloride itself.
Holladay, U.S. Pat. No. 5,733,590, teaches a slow release non-protein nitrogen liquid feed supplement that is made by mixing a 38 wt. % calcium chloride solution with dry urea. Liquids are expensive to ship and require greater care in handling and packing.
Watkins et al., U.S. Pat. No. 4,283,423 discloses a homogeneous urea containing composition as an animal feed supplement. Urea and particular forms of calcium sulfate are mixed and pelletized by compression compaction. In other embodiments, the urea-calcium sulfate constitutes animal feed supplements to be blended with non-hygroscopic nutrients such as calcium phosphate.
Calcium Sulfate and Calcium Phosphate are not as readily soluble and therefore not an easily available source of calcium.
In a promotional paper written by the SODA Company out of Monaco, a feed supplement is disclosed that is a dry calcium chloride using a coating agent of fatty acids.
None of these references, however, teach or suggest a core of a calcium-containing material, which is hygroscopic or deliquescent, combined with other nutrients and protected from moisture intake by a less hygroscopic, soluble non-calcium coating material.